"""Global database feature support policy.

Provides decorators to mark tests requiring specific feature support from the
target database.

External dialect test suites should subclass SuiteRequirements
to provide specific inclusion/exlusions.

"""

from . import exclusions, config


class Requirements(object):
    def __init__(self, config):
        self.config = config

    @property
    def db(self):
        return config.db

class SuiteRequirements(Requirements):

    @property
    def create_table(self):
        """target platform can emit basic CreateTable DDL."""

        return exclusions.open()

    @property
    def drop_table(self):
        """target platform can emit basic DropTable DDL."""

        return exclusions.open()

    @property
    def foreign_keys(self):
        """Target database must support foreign keys."""

        return exclusions.open()

    @property
    def on_update_cascade(self):
        """"target database must support ON UPDATE..CASCADE behavior in
        foreign keys."""

        return exclusions.open()

    @property
    def deferrable_fks(self):
        return exclusions.closed()

    @property
    def on_update_or_deferrable_fks(self):
        # TODO: exclusions should be composable,
        # somehow only_if([x, y]) isn't working here, negation/conjunctions
        # getting confused.
        return exclusions.only_if(
                    lambda: self.on_update_cascade.enabled or self.deferrable_fks.enabled
                )


    @property
    def self_referential_foreign_keys(self):
        """Target database must support self-referential foreign keys."""

        return exclusions.open()

    @property
    def foreign_key_ddl(self):
        """Target database must support the DDL phrases for FOREIGN KEY."""

        return exclusions.open()

    @property
    def named_constraints(self):
        """target database must support names for constraints."""

        return exclusions.open()

    @property
    def subqueries(self):
        """Target database must support subqueries."""

        return exclusions.open()

    @property
    def offset(self):
        """target database can render OFFSET, or an equivalent, in a SELECT."""

        return exclusions.open()

    @property
    def boolean_col_expressions(self):
        """Target database must support boolean expressions as columns"""

        return exclusions.closed()

    @property
    def nullsordering(self):
        """Target backends that support nulls ordering."""

        return exclusions.closed()

    @property
    def standalone_binds(self):
        """target database/driver supports bound parameters as column expressions
        without being in the context of a typed column.

        """
        return exclusions.closed()

    @property
    def intersect(self):
        """Target database must support INTERSECT or equivalent."""
        return exclusions.closed()

    @property
    def except_(self):
        """Target database must support EXCEPT or equivalent (i.e. MINUS)."""
        return exclusions.closed()

    @property
    def window_functions(self):
        """Target database must support window functions."""
        return exclusions.closed()

    @property
    def autoincrement_insert(self):
        """target platform generates new surrogate integer primary key values
        when insert() is executed, excluding the pk column."""

        return exclusions.open()

    @property
    def empty_inserts(self):
        """target platform supports INSERT with no values, i.e.
        INSERT DEFAULT VALUES or equivalent."""

        return exclusions.only_if(
                    lambda: self.config.db.dialect.supports_empty_insert or \
                        self.config.db.dialect.supports_default_values,
                    "empty inserts not supported"
                )

    @property
    def insert_from_select(self):
        """target platform supports INSERT from a SELECT."""

        return exclusions.open()

    @property
    def returning(self):
        """target platform supports RETURNING."""

        return exclusions.only_if(
                lambda: self.config.db.dialect.implicit_returning,
                "'returning' not supported by database"
            )

    @property
    def denormalized_names(self):
        """Target database must have 'denormalized', i.e.
        UPPERCASE as case insensitive names."""

        return exclusions.skip_if(
                    lambda: not self.db.dialect.requires_name_normalize,
                    "Backend does not require denormalized names."
                )

    @property
    def multivalues_inserts(self):
        """target database must support multiple VALUES clauses in an
        INSERT statement."""

        return exclusions.skip_if(
                    lambda: not self.db.dialect.supports_multivalues_insert,
                    "Backend does not support multirow inserts."
                )


    @property
    def implements_get_lastrowid(self):
        """"target dialect implements the executioncontext.get_lastrowid()
        method without reliance on RETURNING.

        """
        return exclusions.open()

    @property
    def emulated_lastrowid(self):
        """"target dialect retrieves cursor.lastrowid, or fetches
        from a database-side function after an insert() construct executes,
        within the get_lastrowid() method.

        Only dialects that "pre-execute", or need RETURNING to get last
        inserted id, would return closed/fail/skip for this.

        """
        return exclusions.closed()

    @property
    def dbapi_lastrowid(self):
        """"target platform includes a 'lastrowid' accessor on the DBAPI
        cursor object.

        """
        return exclusions.closed()

    @property
    def views(self):
        """Target database must support VIEWs."""

        return exclusions.closed()

    @property
    def schemas(self):
        """Target database must support external schemas, and have one
        named 'test_schema'."""

        return exclusions.closed()

    @property
    def sequences(self):
        """Target database must support SEQUENCEs."""

        return exclusions.only_if([
                lambda: self.config.db.dialect.supports_sequences
            ], "no sequence support")

    @property
    def sequences_optional(self):
        """Target database supports sequences, but also optionally
        as a means of generating new PK values."""

        return exclusions.only_if([
                lambda: self.config.db.dialect.supports_sequences and \
                    self.config.db.dialect.sequences_optional
            ], "no sequence support, or sequences not optional")





    @property
    def reflects_pk_names(self):
        return exclusions.closed()

    @property
    def table_reflection(self):
        return exclusions.open()

    @property
    def view_reflection(self):
        return self.views

    @property
    def schema_reflection(self):
        return self.schemas

    @property
    def primary_key_constraint_reflection(self):
        return exclusions.open()

    @property
    def foreign_key_constraint_reflection(self):
        return exclusions.open()

    @property
    def index_reflection(self):
        return exclusions.open()

    @property
    def unique_constraint_reflection(self):
        """target dialect supports reflection of unique constraints"""
        return exclusions.open()

    @property
    def unbounded_varchar(self):
        """Target database must support VARCHAR with no length"""

        return exclusions.open()

    @property
    def unicode_data(self):
        """Target database/dialect must support Python unicode objects with
        non-ASCII characters represented, delivered as bound parameters
        as well as in result rows.

        """
        return exclusions.open()

    @property
    def unicode_ddl(self):
        """Target driver must support some degree of non-ascii symbol names."""
        return exclusions.closed()

    @property
    def datetime(self):
        """target dialect supports representation of Python
        datetime.datetime() objects."""

        return exclusions.open()

    @property
    def datetime_microseconds(self):
        """target dialect supports representation of Python
        datetime.datetime() with microsecond objects."""

        return exclusions.open()

    @property
    def datetime_historic(self):
        """target dialect supports representation of Python
        datetime.datetime() objects with historic (pre 1970) values."""

        return exclusions.closed()

    @property
    def date(self):
        """target dialect supports representation of Python
        datetime.date() objects."""

        return exclusions.open()

    @property
    def date_historic(self):
        """target dialect supports representation of Python
        datetime.datetime() objects with historic (pre 1970) values."""

        return exclusions.closed()

    @property
    def time(self):
        """target dialect supports representation of Python
        datetime.time() objects."""

        return exclusions.open()

    @property
    def time_microseconds(self):
        """target dialect supports representation of Python
        datetime.time() with microsecond objects."""

        return exclusions.open()

    @property
    def precision_numerics_general(self):
        """target backend has general support for moderately high-precision
        numerics."""
        return exclusions.open()

    @property
    def precision_numerics_enotation_small(self):
        """target backend supports Decimal() objects using E notation
        to represent very small values."""
        return exclusions.closed()

    @property
    def precision_numerics_enotation_large(self):
        """target backend supports Decimal() objects using E notation
        to represent very large values."""
        return exclusions.closed()

    @property
    def precision_numerics_many_significant_digits(self):
        """target backend supports values with many digits on both sides,
        such as 319438950232418390.273596, 87673.594069654243

        """
        return exclusions.closed()

    @property
    def precision_numerics_retains_significant_digits(self):
        """A precision numeric type will return empty significant digits,
        i.e. a value such as 10.000 will come back in Decimal form with
        the .000 maintained."""

        return exclusions.closed()

    @property
    def text_type(self):
        """Target database must support an unbounded Text() "
        "type such as TEXT or CLOB"""

        return exclusions.open()

    @property
    def empty_strings_varchar(self):
        """target database can persist/return an empty string with a
        varchar.

        """
        return exclusions.open()

    @property
    def empty_strings_text(self):
        """target database can persist/return an empty string with an
        unbounded text."""

        return exclusions.open()

    @property
    def update_from(self):
        """Target must support UPDATE..FROM syntax"""
        return exclusions.closed()

    @property
    def update_where_target_in_subquery(self):
        """Target must support UPDATE where the same table is present in a
        subquery in the WHERE clause.

        This is an ANSI-standard syntax that apparently MySQL can't handle,
        such as:

        UPDATE documents SET flag=1 WHERE documents.title IN
            (SELECT max(documents.title) AS title
                FROM documents GROUP BY documents.user_id
            )
        """
        return exclusions.open()

    @property
    def mod_operator_as_percent_sign(self):
        """target database must use a plain percent '%' as the 'modulus'
        operator."""
        return exclusions.closed()

    @property
    def unicode_connections(self):
        """Target driver must support non-ASCII characters being passed at all."""
        return exclusions.open()

    @property
    def skip_mysql_on_windows(self):
        """Catchall for a large variety of MySQL on Windows failures"""
        return exclusions.open()

    def _has_mysql_on_windows(self):
        return False

    def _has_mysql_fully_case_sensitive(self):
        return False
